Video signals, such as composite video signals, include synchronization pulses to indicate where a video decoder should place the active video information contained in the video signal. For example, horizontal synchronization pulses synchronize the horizontal placement of the video picture information at the display device, while vertical synchronization pulses synchronize the vertical placement of the picture information. The synchronization pulses are represented by a particular level or magnitude of the video signal relative to the video picture information. For example, in a composite video signal, lower magnitude portions of the signal referred to as synch tips represent the horizontal and video synchronization pulses, where the video signal level is relatively lower than the signal levels representing the active video information.
However, while the relative levels of the synchronization pulses and the active video information are typically known, the absolute levels of the video signal can vary depending on the source of the video signal. Accordingly, the synchronization pulses can be difficult to decode directly using a fixed threshold. In some video decoders this is overcome by clamping the video signal and the threshold level prior to detection of the synchronization pulses. However, the clamping and decoding circuitry can consume an undesirable amount of circuit area.
Accordingly, there is a need for an improved device and method for detecting synchronization pulses in a signal.